To pressure cooker bomb stuffed into backpacks allegedly detonated by two Brothers. Says the release of the alleged Boston bombers photos on April 18 the world is associated the marathon attack with the number two until today. When as ABC's chief investigative correspondent Brian Ross discovers authorities charged three more men in the investigation men they say may have tried to protect demand. Considered by many. To be public enemy number one. The FBI has been suspicious of the friends since the day of the -- When swat teams raided the college campus and agents took two of them into custody on immigration charges. Those two both from Kazakhstan I was about -- -- -- and diets got to buy off. Had traveled with the -- hollers and I have to New York last year proudly posing in the snapshot. Their lawyers said their clients had done nothing wrong outside the courthouse but the two appeared before a federal -- Straight and DS -- -- I have absolutely denies the charges as we've said from the very beginning. He assisted the FBI in this investigation we got. And in -- YouTube video he posted on line appeared to be an articulate intelligent young next. The small little -- -- season. You know ten years of rigorous work. But tonight the FBI paints a very sinister picture agents say -- -- friends recognized him immediately. When those surveillance photos of the suspects were made public. We consider them to be it armed and extremely dangerous and decided to help -- by getting rid of potential evidence. The government allegations as far as that he saw a -- recognize them. Immediately we dispute and we'll be looking forward to proving our case in -- Court but the FBI says one of the teams texted -- and asked if he was the bomber. LO well to -- responded laughing out loud and then another exchange come to -- a room and take whatever you want. The FBI says the three went to -- room that night the pine dale dormitory. Down this hall on the third floor to rule number 7341. According to the complaint they took a backpack containing fireworks with the powder removed and Joseph -- laptop computer. That night there was the violent confrontation with authorities and the manhunt for your -- began. It was then the next morning the FBI says that one of the friends went behind their apartment building in New Bedford. And dumped the backpack and fireworks in this dumpster. He did not know that those items were involved in a bombing or of any interest in a bombing or any evidence of value. But the dumpsters contents ended up at a landfill -- the FBI search for three days and found what it says where those fireworks. The FBI alleges the three friends tried to -- -- like this is crazy that this is -- success this season. Makes sense I don't believe they've seen so both -- -- -- -- -- that that it -- it. The FBI believes the powder from the fireworks and that that -- was used to make the bombs. There's no indication so far that the friends knew about the plot in advance but in a footnote in the criminal complaint. One of the friends is quoted as saying that -- -- told him a month before the bombing that he knew how to make a Bob.

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